Vacuum cleaners that utilise cyclonic separation apparatus are well known. EP2413767, EP2674087 and EP 2764810 each describe vacuum cleaning apparatus that utilise cyclone separation techniques.
In general, cyclonic separation apparatus functions by admitting a dirty airflow into a cyclone chamber via a tangential inlet which causes the airflow to follow a spiral or helical path within the cyclone chamber. This causes the dirt and debris contained within the airflow to separate, allowing the dirt to be collected and removed. Generally, the separated dirt and debris collects in a dirt collection chamber located beneath the cyclone chamber. The dirt collection chamber may be transparent so that the user is able to view the amount of dirt and debris that has been collected. The user is then able to determine when it is necessary to empty the dirt collection chamber.
The dirt collection chamber may not be entirely visible to the user, particularly during normal use. For example, the cyclonic separation apparatus may be mounted within a main body of the vacuum cleaner such that part of the dirt collection chamber is obscured from view during normal use. A problem may then arise should dirt collect only in that part obscured from view. In particular, the user would continue to use the vacuum cleaner causing the dirt collection chamber to become over-filled, resulting in a reduced efficiency of the cyclone. Additionally dirt may be re-entrained into the clean air outflow.